Is your feature request related to a problem or challenge?

As discussed here: #1650 (comment)

We should have a TaskWriter that can write either partitioned or unpartitioned data.

Describe the solution you'd like

• TaskWriter should be able to write both partitioned and unpartitioned data
• TaskWriter should be generic, and the implementations should be engine-specific
• For partitioned data, TaskWriter should split the incoming record batch by partition, and assign the (partition_key, splitted batch) pairs to PartitioningWriter

Willingness to contribute

I can contribute to this feature independently